Here is the full list of all 46 Squids Odyssey achievements.
Defeat 50 enemies with a jellyfish
Level up a squid to level 25
Unlock all helmets in your inventory
Hit 6 enemies in one stomp attack
Unlock all seahorses
Complete Chapter 8
Unlock all cursed helmets in your inventory
Use 10 miracle tentacles
Recruit Oktoku
Finish "The Spirit of the West" in 1 turn without inventory items
Complete Chapter 6
Complete Chapter 7
Recruit Magnus
Each squid should bounce on something at each turn in mission "Holding Ground"
Recruit Cleef
Finish mission "back to the wall" in 2 turns
Complete Chapter 5
Defeat 500 enemies
Level up all squids to level 10
Complete Chapter 4
Recruit Brad
Recruit Kapono
Complete Chapter 3
Heal 500 HP with a healer squid
Recruit Ronimo
Complete Chapter 2
Level up a squid to level 10
Defeat 10 enemies in one turn
Invoke a mighty kraken
Push an enemy in a hole with a shoot attack in mission "Lady in the Water"
Recruit Calamary Jane
Recruit Jammer
Complete Chapter 1
Beat the first Guardian
Recruit Venus
Give a 5 combo melee hit
Recruit Vesper
Play a mission with the redemption hat
Recruit Clint
Recruit Sammo
Defeat 50 enemies on a Seahorse
Do 10 combos in mission "The Iron Throne"
Level up all squids from to level 25
Get 3 stars for all story missions
Get 3 stars for all bonus missions
Complete all missions in Pro Mode